Pressure based wireless sensor and applications thereof

ABSTRACT

A wireless sensor includes an antenna, a tuning circuit, a pressure sensing circuit, a processing module, and a transmitter. Collectively, the pressure sensing circuit, the antenna, and the tuning circuit have one or more radio frequency (RF) characteristics and the pressure sensing circuit causes the RF characteristic(s) to vary with varying sensed pressures. The processing module detects a variance of the RF characteristic(s) from a desired value. In response to the detecting of the variance, the processing module adjusts the tuning circuit to substantially re-establish the desired value of the RF characteristic(s). The processing module generates a message regarding the adjusting of the tuning circuit, wherein a level of the adjusting is representative of a variance of pressure sensed by the pressure sensing circuit. The transmitter transmits the message.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application also claims prioritypursuant to 35 U.S.C. §120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 15/157,723, entitled, “PRESSURE BASED WIRELESSSENSOR AND APPLICATIONS THEREOF”, filed on May 18, 2016, which claimspriority pursuant to 35 U.S.C. §119(e) to U.S. Provisional ApplicationNo. 62/163,143, entitled “RFID TAGS AND SENSORS”, filed May 18, 2015,both of which are hereby incorporated herein by reference in theirentirety and made part of the present U.S. Utility Patent Applicationfor all purposes.

The present U.S. Utility Patent Application also claims prioritypursuant to 35 U.S.C. §120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 14/869,940, entitled “RADIO FREQUENCYIDENTIFICATION (RFID) TAG(S) and SENSOR(S)”, filed Sep. 29, 2015, whichclaims priority pursuant to 35 U.S.C. §119(e) to U.S. ProvisionalApplication No. 62/057,186, entitled “RADIO FREQUENCY IDENTIFICATION(RFID) TAGS AND SENSORS”, filed Sep. 29, 2014; and U.S. ProvisionalApplication No. 62/057,187, entitled “METHOD AND APPARATUS FOR IMPEDANCEMATCHING USING DITHERING”, filed Sep. 29, 2014, all of which are herebyincorporated herein by reference in their entirety and made part of thepresent U.S. Utility Patent Application for all purposes.

U.S. Utility patent application Ser. No. 15/157,723 also claims prioritypursuant to 35 U. S.C. §120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 14/869,940, entitled “RADIO FREQUENCYIDENTIFICATION (RFID) TAG(S) and SENSOR(S)”, filed Sep. 29, 2015, whichclaims priority pursuant to 35 U.S.C. §119(e) to U.S. ProvisionalApplication No. 62/057,186, entitled “RADIO FREQUENCY IDENTIFICATION(RFID) TAGS AND SENSORS”, filed Sep. 29, 2014; and U.S. ProvisionalApplication No. 62/057,187, entitled “METHOD AND APPARATUS FOR IMPEDANCEMATCHING USING DITHERING”, filed Sep. 29, 2014, all of which are herebyincorporated herein by reference in their entirety and made part of thepresent U.S. Utility Patent Application for all purposes

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

NOT APPLICABLE

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to wireless communications and moreparticularly to wireless sensors and applications thereof.

Description of Related Art

Wireless communication systems are known to include wirelesstransceivers that communication directly and/or over a wirelesscommunication infrastructure. In direct wireless communications, a firstwireless transceiver includes baseband processing circuitry and atransmitter to convert data into a wireless signal (e.g., radiofrequency (RF), infrared (IR), ultrasound, near field communication(NFC), etc.). Via the transmitter, the first wireless transceivertransmits the wireless signal. When a second wireless transceiver is inrange (e.g., is close enough to the first wireless transceiver toreceive the wireless signal at a sufficient power level), it receivesthe wireless signal via a receiver and converts the signal intomeaningful information (e.g., voice, data, video, audio, text, etc.) viabaseband processing circuitry. The second wireless transceiver maywirelessly communicate back to the first wireless transceiver in asimilar manner.

Examples of direct wireless communication (or point-to-pointcommunication) include walkie-talkies, Bluetooth, ZigBee, RadioFrequency Identification (RFID), etc. As a more specific example, whenthe direct wireless communication is in accordance with RFID, the firstwireless transceiver may be an RFID reader and the second wirelesstransceiver may be an RFID tag.

For wireless communication via a wireless communication infrastructure,a first wireless communication device transmits a wireless signal to abase station or access point, which conveys the signal to a wide areanetwork (WAN) and/or to a local area network (LAN). The signal traversesthe WAN and/or LAN to a second base station or access point that isconnected to a second wireless communication device. The second basestation or access point sends the signal to the second wirelesscommunication device. Examples of wireless communication via aninfrastructure include cellular telephone, IEEE 802.11, public safetysystems, etc.

In many situations, direct wireless communication is used to gatherinformation that is then communicated to a computer. For example, anRFID reader gathers information from RFID tags via direct wirelesscommunication. At some later point in time (or substantiallyconcurrently), the RFID reader downloads the gathered information to acomputer via a direct wireless communication or via a wirelesscommunication infrastructure.

For instance, in automobiles, wireless tire pressure monitoring sensorsare used to provide tire pressure information to an automobile'scomputer. The sensors may indirectly or directly sense tire pressure.For example, indirect sensing calculates tire pressure from measuredrevolutions of the tire via the sensor. As another example, directsensing measures the tire pressure from inside the tire. Direct sensingprovides a more accurate measure of tire pressure than indirect sensing,but does so at a cost. In particular, direct wireless sensors include abattery and micro-electromechanical semiconductor (MEMS) circuitry tosense the tire pressure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a wirelesscommunication system in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a wirelesscommunication system within a vehicle in accordance with the presentinvention;

FIG. 3 is a schematic block diagram of an embodiment of a wireless datacollecting device and a wireless sensor in accordance with the presentinvention;

FIG. 4 is a schematic block diagram of another embodiment of a wirelesssensor in accordance with the present invention;

FIG. 5 is a schematic block diagram of another embodiment of a wirelesssensor in accordance with the present invention;

FIG. 6 is a schematic block diagram of an embodiment of a pressuresensing circuit of a wireless sensor in accordance with the presentinvention;

FIG. 7 is a schematic block diagram of another embodiment of a pressuresensing circuit of a wireless sensor in accordance with the presentinvention;

FIG. 8 is a schematic block diagram of another embodiment of a pressuresensing circuit of a wireless sensor in accordance with the presentinvention;

FIG. 9 is a schematic block diagram of another embodiment of a pressuresensing circuit of a wireless sensor in accordance with the presentinvention;

FIG. 10 is a schematic block diagram of an example of a wireless sensorreceiving an RF signal in accordance with the present invention; and

FIG. 11 is a logic diagram of an embodiment of a method for calibratinga wireless sensor in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a wirelesscommunication system 10 that includes three categories of devices: datageneration 12, data collecting 14, and data processing 16. As shown, thedata generation category 12 includes wireless sensors 18-24. Thewireless sensors 18-24 may be implemented in a variety of ways toachieve a variety of data generation functions. For example, a wirelesssensor includes a passive RFID topology and a sensing feature to senseone or more environmental conditions (e.g., moisture, temperature,pressure, humidity, altitude, sonic wave (e.g., sound), human contact,surface conditions, tracking, location, etc.) associated with an object(e.g., a box, a personal item (e.g., clothes, diapers, etc.), a pet, anautomobile component, an article of manufacture, an item in transit,etc.). As another example, the wireless sensor includes an active RFIDtopology and a sensing feature. As yet another example, the wirelesssensor includes processing circuitry and a transceiver for use with apersonal area network (e.g., Bluetooth), a local area network (e.g.,WiFi, local wireless area network), and/or a wide area network (e.g.,cellular voice and/or data).

The data collecting category 14 includes stationary wireless collectingdevices 26 and/or portable wireless data collecting devices 28. Theconstruct of a wireless data collecting device 26 and/or 28 is at leastpartially dependent on the data generation devices of category 12. Forexample, when a wireless sensor includes an RFID topology, the wirelessdata collecting device 26 and/or 28 is an RFID reader. As a specificexample, the portable wireless data collecting device 28 is a hand-heldRFID reader and the stationary wireless collecting device 26 is a RFIDreader mounted in a particular location (e.g., on an assembly line of amanufacturing process).

In general, the wireless sensors 18-24 generate data that is wirelesslycommunicated to the wireless data collecting devices 26 and/or 28. Awide variety of wireless communication protocols and/or standards may beused. For example, the wireless communication is in accordance with oneor more RFID wireless communication standards and/or protocols. Asanother example, the wireless communication is in accordance withBluetooth, ZigBee, IEEE 802.11, etc.

The data processing category 16 includes one or more computing devices30. The computing device 30 may be a personal computer, a tabletcomputer, a laptop, a mainframe computer, and/or a server. The computingdevice 30 communicates with the wireless data collecting devices via awired and/or wireless local area network, wide area network, orpoint-to-point network.

As an example, the wireless communication system 10 is deployed in afactory that assembles a product from multiple components in multiplestages occurring in multiple locations within the factory. Each of thecomponents includes a wireless sensor that identifies the component andmay further generate data regarding one or more environmental conditionsof the component. In some locations within the factory, stationarywireless data collecting devices are positioned to communicate with thewireless sensors in their proximal area. In other locations of thefactory, employees use the portable wireless data collecting devices 28to communication with the wireless sensors in their proximal area.

As the wireless data collecting devices 26 and 28 communicate with thewireless sensors 18-24, they collect data from the sensors and relay thedata to the computing device 30. The computing device processes the datato determine a variety of information regarding the assembly of theproducts, defects, efficiency, etc.

While the categories 12-16 of the wireless communication system areshown to have separate devices, a device may span multiple categories.For example, a data collecting device includes functionality to processat least some of the data it collects. As another example, a wirelesssensor includes functionality to store and/or interpret the data it iscollecting.

FIG. 2 is a schematic block diagram of an embodiment of a wirelesscommunication system within a vehicle. The wireless communication systemincludes a plurality of wireless sensors 20, one or more wireless datacollecting devices 26, and a computing device 30. In an exampleembodiment, the wireless sensors 20 are passive sensors having an RFIDtopology that are positioned within tires of the vehicle; the wirelessdata collecting device 26 is an RFID reader, or multiple RFID readers;and the computing device 30 is the on-board computer of the vehicle.

In an example of operation, the wireless data collecting device 26transmits a radio frequency (RF) signal to a wireless sensor 20 inaccordance with one or more RFID communication protocols. The wirelesssensor 20 converts the RF signal into a DC supply voltage that is usedto power the other components of the wireless sensor, including apressure sensing circuit. The pressure sensing circuit measures pressurewithin its respective tire, which is communicated back to the wirelessdata collecting device 26.

The wireless data collecting device 26 communicates with the otherwireless sensors 20 in the same way to collect tire pressuremeasurements of the other tires. The wireless data collecting device 26provides the tire pressure measurements to the computing device 30,which processes the data. For instance, the computing device mayindicate that a tire pressure is too low, too high, or within anacceptable range. Note that a tire may include more than one sensor suchmultiple pressure measurements per tire are taken and processed.

FIG. 3 is a schematic block diagram of another embodiment of a wirelessdata collecting device 26-28 and a wireless sensor 18-24. The wirelesssensor 18-24 includes a power harvesting circuit 32, a processing module34, memory 36, a receiver section 38, a transmitter section 40, anantenna structure 42, a power detection circuit 56, a pressure sensingcircuit 58, and a tuning circuit 60. The wireless data collecting deviceincludes an antenna structure 44, a transmitter 46, a receiver 48, atransmit/receive splitter or switch (T/R), a processing module 50,memory 52, and an interface 54. The interface 54 includes firmware(e.g., software and hardware) to communicate with the computing device30 via a wired and/or wireless LAN and/or WAN.

In an example of operation, the wireless sensor is a passive RFID tagand the wireless data collecting device is an RFID reader. The passiveRFID tag is associated with an object and an object identifier is storedin the memory 36 of the wireless sensor. For the RFID reader tocommunicate with the passive RFID tag, the tag first generates a powersupply voltage (or multiple power supply voltages) from the RF (radiofrequency) signal 43 transmitted from the RFID reader. For example, theRF signal 43 is a continuous wave signal and uses amplitude shift keying(ASK) or other amplitude-based modulation scheme to convey data.

The power harvesting circuit 32 receives the RF signal 43 via theantenna 42 and converts it into one or more supply voltages (Vs). Thesupply voltage(s) power the other components (e.g., 34-40, 56) so thatthey perform their specific tasks. For instance, the receiver 38 isoperable to convert an inbound message received from the RFID readerinto a baseband signal that it provides to the processing module 34. Theprocessing module 34 processes the baseband signal and, whenappropriate, generates a response that is subsequently transmitted viathe antenna 42 by the transmitter 40. For example, the inbound messageinstructs the wireless sensor to provide a respond with a pressuremeasurement and the stored ID of the object.

To obtain a pressure measurement, the pressure sensing circuit 58 sensesthe pressure within an area (e.g., within a tire of an automobile). Forexample, as the pressure sensing circuit 58 is subjected to differentpressures (e.g., force per area measured in pounds per square inch orother units), its electrical characteristics change. For instance, acapacitance, an inductance, an impedance, a resonant frequency, or othercharacteristic changes (e.g., increases or decreases).

The electrical characteristics change of the pressure sensing circuit 58causes a change in an RF characteristic of the combination of theantenna 42, the tuning circuit 60, and the pressure sensing circuit 58.Note that an RF characteristic includes an impedance (e.g., an inputimpedance) at a frequency (e.g., carrier frequency of the RF signal 43),a resonant frequency (e.g., of the turning circuit and/or antenna), aquality factor (e.g., of the antenna), and/or a gain. As a specificexample, the resonant frequency has changed from a desired resonantfrequency (e.g., matching the carrier frequency of the RF signal 43) asresult of the sensed pressure.

The processing module 34 detects a variance of the one or more RFcharacteristics from a desired value (e.g., the resonant frequencychanges from a desired frequency that corresponds to the carrierfrequency of the RF signal 43). When the processing module detects thevariance, it adjusts the tuning circuit to substantially re-establishthe desired value of the one or more RF characteristics. For example,the tuning circuit 60 includes an inductor and a capacitor, one of whichis adjusted to change the resonant frequency back to the desired value.

The processing module 34 determines the amount of adjustment of thetuning circuit 60 and converts the amount of adjustment into a digitalvalue. The digital value is representative of the pressure sensed by thepressure sensing circuit 58. The processing module 34 generates amessage regarding the adjusting of the tuning circuit (e.g., the messageincludes the digital value or an actual pressure measurement if theprocessing module performs a digital value to pressure measurementconversion function). The transmitter transmits the message to the datacollecting device via the antenna 42 or other antenna (not shown in FIG.3).

Before the processing module processes the sensed environmentalcondition, it may perform a power level adjustment. For example, thepower detection circuit 56 detects a power level of the received RFsignal 43. In one embodiment, the processing module interprets the powerlevel and communicates with the RFID reader to adjust the power level ofthe RF signal 43 to a desired level (e.g., optimal for accuracy indetecting the environmental condition). In another embodiment, theprocessing module includes the received power level data with theenvironmental sensed data it sends to the RFID reader so that the readercan factor the power level into the determination of the extent of theenvironmental condition.

The processing module 34 may be further operable to perform acalibration function when the pressure in which the wireless sensor isknown (e.g., in a room at a certain altitude, in a calibration chamberhaving a set pressure, etc.). For example, the processing module 34receives a calibration request from a data collecting device. Inresponse, the processing module adjusts the tuning circuit to establishthe desired value of the RF characteristic(s) (e.g., resonant frequency,input impedance, quality factor, gain, etc.). The processing module thenrecords a level of the adjusting of the tuning circuit to represent apressure calibration of the wireless sensor (e.g., records a digitalvalue). The processing module may communicate the calibration value tothe data collecting device as part of the calibration process or send italong with the digital value of a pressure measurement.

FIG. 4 is a schematic block diagram of another embodiment of a wirelesssensor 18-24 that includes the power harvesting circuit 32, theprocessing module 34, memory 36, the receiver section 38, thetransmitter section 40, a first antenna structure 42, a second antennastructure 45, one or more power detection circuits 56, a pressuresensing circuit 58, a first tuning circuit 60-1, and a second tuningcircuit 60-2. Each of the first and second antenna structures 42 and 45include an antenna (e.g., monopole, dipole, helical, etc.) and mayfurther include impedance matching circuitry, filtering circuitry,and/or one or more additional antennas for beamforming, diversity,and/or other antenna array configurations and/or applications.

In this embodiment, the pressure sensing is separated from the powerharvesting and communication. For instance, the pressure sensing circuit58 is operably coupled to the first antenna structure 42, where operablycoupled means, in addition to as otherwise defined herein, in closephysical proximity to affect RF characteristics of the antenna 42 and/ortuning circuit 60-1 and/or electrically connected to the antenna and/ortuning circuit. The pressure sensing circuit 58, the processing module34, and the tuning circuit 60-1 function as described herein to generatea digital representation of a pressure measurement.

The pressure sensing side of the wireless sensor may further include aseparate power detection circuit 56 to provide power measurements to theprocessing module regarding the RF signal received via antenna 42. Theprocessing module 34 may use the power information to interpret the RFcharacteristic changes or may provide a digital representation ofreceived power of the antenna 42 to the data collection device. Forexample, the processing module 34 calibrates pressure sensing based on aparticular input power and a known pressure level. When a pressuremeasurement is taken and the input power deviates from the particularinput power of calibration, the processing module 34 either factors thatinto the pressure sensing measurement, requests a transmit poweradjustment by the data collecting device, and/or provides a digitalrepresentation of the received input power and a digital representationof the pressure measurement to the data collecting device.

The second antenna structure 45 supports the separate power harvestingand communication. On this side of the wireless sensor, the powerharvesting circuit 32, the power detection circuit 56 (which is optionalfor this side of the wireless sensor), the second tuning circuit 60-2,the receiver 38, the transmitter 40, and the processing module 34function to optimize the generation of power and communication with thedata collecting device. For instance, the processing module 34 adjuststhe tuning circuit 60-2 to align its resonant frequency with thefrequency of the RF signal 43 allowing for more efficient powerharvesting.

With the separation of sensing from power harvesting and communication,the first antenna structure 42 may be located in an area that has lessreception of the RF signal than the second antenna structure 45. Forexample, the first antenna structure 42 and the pressure sensing circuitare positioned on a printed circuit board that is mounted within a tirewhere the steel rim and the steel cabling of the tire limit reception ofthe RF signal 43 by the antenna 42. The second antenna 45 is locatedoutside of the tire (e.g., along the stem of the tire or elsewhere) andthus the rim and the tire do not limit its reception of the RF signal.

FIG. 5 is a schematic block diagram of another embodiment of a wirelesssensor 18-24 that is similar to the wireless sensor of FIG. 4 with theaddition of a temperature sensor 65. When the wireless sensor is poweredup (e.g., the power harvesting circuit 32 is producing a power supplyvoltage), the temperature sensor 65 is enabled to measure temperature ofits environment. The temperature sensor 65 may have a variety ofimplementations. For example, the temperature sensor 65 has athermocouple topology to produce a voltage representative oftemperature. As another example, the temperature sensor 65 includes atemperature sensing diode. As another example, the temperature sensor 65includes circuitry that, as temperature varies, causes an RFcharacteristic of the antenna and/or tuning circuit to vary.

FIG. 6 is a schematic block diagram of an embodiment of a pressuresensing circuit 58 that includes a metallic diaphragm 58-1 andcapacitive plates 58-2 and 58-3, which form a variable capacitancecircuit. Capacitive plate 58-2 with the diaphragm 58-1 form a firstcapacitance C1 and capacitive plate 58-3 with the diaphragm 58-1 form asecond capacitance C2. The total capacitance of the pressure sensingcircuit 58 is the series combination of C1 and C2. The first capacitiveplate 58-2 is coupled to a first antenna element of antenna 42 (which isshown as a dipole antenna) and the second capacitive plate 58-3 iscoupled to a second antenna element of the antenna 42.

The first capacitive plate 58-2, the second capacitive plate 58-3, andthe diaphragm 58-1 are sized and spaced to provide specific capacitancevalues for C1 and C2. The specific capacitance values are based on thecarrier frequency of the RF signal and a desired amount of change of theone or more RF characteristics of the front-end of the sensor 18-24. Forexample, at a carrier frequency of 900 MHz, the input impedance of thefront-end is 50 Ohms, and a desired change is about 25%, then theimpedance of the series combination at 900 MHz is about 12.5 Ohms (e.g.,25% of 50 Ohms) and the series capacitance is about 14 pF.

When the diaphragm 58-1 is compressed, the total capacitance increases,which causes a change in the one or more RF characteristics of thefront-end (e.g., impedance). When the antenna 42 receives an RF signal(with the diaphragm compressed), the power detection circuit 56 andpower harvesting circuit function as previously described. Theprocessing module 34, which includes a detection circuit 35 and acontroller 37, receives a power indication 33 (e.g., the input power,the supply voltage, a supply current, input voltage, etc.) thatcorresponds to the input power of the RF signal. The detection circuit35 adjusts the varactor of the tuning circuit 60, which further includesan inductor, to change the one or more RF characteristics. When thepower indication 33 indicates a maximum, or near maximum, power level(voltage, and/or current without saturation), of the front-end of thesensor (e.g., the antenna 4, the tuning circuit 60, and/or the pressuresensing circuit 58) is in resonance, or near resonance, with the carrierfrequency of the RF signal. The controller 37 determines the amount thatthe tuning circuit was adjusted and created a digital representationthereof. The digital representation may be stored in memory 36 and/ortransmitted to a data collecting device 26-28.

FIG. 7 is a schematic block diagram of another embodiment of a pressuresensing circuit 58 that includes a tuning loop 58-5 and a diaphragm58-4. The tuning loop 58-5 is coupled to the antenna elements of theantenna 42. The diaphragm 58-4 is a metal plate that, as it iscompressed towards the tuning loop 58-5, decreases the inductance of thetuning loop 58-5. A change in the inductance of the tuning loop 58-5causes a change in the one or more RF characteristics of the front-end.As such, changes in the inductance corresponds to varying pressuresapplied to the diagram.

FIG. 8 is a schematic block diagram of another embodiment of a pressuresensing circuit 58 that is similar to the pressure sensing circuit ofFIG. 6 with a puck diaphragm 58-6 replacing the diaphragm 58-1. The puckdiaphragm 58-6 is comprised of a metal material that includes ahermetically sealed core. The core may be a vacuum core, a gas filledcore (e.g., a gas with low expansion-contraction over temperature), adry nitrogen filed core, a gasless core, etc. As pressure is applied tothe puck diaphragm 58-6, the total capacitance of the pressure sensingcircuit is reduced, which causes a change in the one or more RFcharacteristics of the front-end. In an embodiment, the bottom surfaceof the puck (e.g., the surface towards the plates 58-2 and 58-3) isthinner than the side walls and top surface (as orientated in thefigure) such that it is the surface that primarily moves in response topressure.

FIG. 9 is a schematic block diagram of another embodiment of a pressuresensing circuit 58 that is similar to the pressure sensing circuit ofFIG. 7 with a puck diaphragm 58-6 replacing the diaphragm 58-4. The puckdiaphragm 58-6 is comprised of a metal material and includes a vacuumcore. As pressure is applied to the puck diaphragm 58-6, the inductanceof the tuning loop 58-5 is increased, which causes a change in the oneor more RF characteristics of the front-end.

FIG. 10 is a schematic block diagram of an example of a wireless sensor18-24 receiving an RF signal 43. A data collecting device transmits theRF signal 43 at a given power level, which may be received by thewireless sense at a received power level ranging from a minimum inputpower to a maximum input power. In an embodiment, the RF signal 43 is acontinuous wave at a given frequency (fc).

In many instances, it is desirable to have the input power level at aparticular level (e.g., the minimum level or other level). For example,the RF characteristic of the antenna and tuning circuit are dependent onthe input power level. As such, the input power level needs to beaccounted for to accurately tune the tuning circuit. In one embodiment,the input power is accounted for by the wireless sensor communicatingwith the data collection device to lower the transmit power of the RFsignal such that the wireless sensor receives it at the desire inputpower level. In another embodiment, the wireless sensor determines theinput power level and provides an indication of the input power levelalong with the tuning circuit adjustment to the data collecting device.

FIG. 11 is a logic diagram of an embodiment of a method for calibratinga wireless sensor in a known environment with known environmentalconditions (e.g., moisture, temperature, pressure, etc.). The methodbegins at step 100 where the power harvesting circuit converts thecontinuous wave signal (e.g., the RF signal 43) into a power supplyvoltage(s). The method continues at step 102 where a determination ismade as to whether there is sufficient power to power the wirelesssensor. For example, a determination is made as to whether the powersupply voltage has reached a desired voltage level. If not, the methodrepeats at step 100.

When there is sufficient power, the method continues at step 104 wherethe processing module adjusts the tuning circuit to change a resonantfrequency (fr) of the input section of the wireless sensor (e.g., theantenna, the tuning circuit, the pressure sensing circuit, thetemperature sensing circuit, and/or other components). Note that, at thestart of calibration, the resonant frequency (fr) of the input sectionof the wireless sensor may be at any frequency within a range offrequencies centered about the carrier frequency of the RF signal (fc).

The method continues at step 106 where a determination is made as towhether the resonant frequency (fr) is substantially aligned with thecarrier frequency (fc). For example, alignment may be determined basedon an interpretation of power levels, voltage levels, and/or currentlevels within the wireless sensor. If not, the method repeats at step104 by further adjusting the tuning circuit (e.g., in the same directionor in an opposition direction). If the frequencies are aligned, themethod continues at step 108 where the wireless sensor is calibrated andthe settings for the tuning circuit are stored as the calibrationsettings. The calibration settings may be stored by the wireless sensor,the data collecting device, and/or computing device.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc., any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

While the transistors in the above described figure(s) is/are shown asfield effect transistors (FETs), as one of ordinary skill in the artwill appreciate, the transistors may be implemented using any type oftransistor structure including, but not limited to, bipolar, metal oxidesemiconductor field effect transistors (MOSFET), N-well transistors,P-well transistors, enhancement mode, depletion mode, and zero voltagethreshold (VT) transistors.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A wireless sensor comprises: an antenna; a tuningcircuit operably coupled to the antenna; a pressure sensing circuitoperably coupled at least one of the antenna and the tuning circuit,wherein the antenna, the tuning circuit, and the pressure sensingcircuit collectively have one or more radio frequency (RF)characteristics and wherein the pressure sensing circuit causes the oneor more RF characteristics to vary with varying sensed pressures; aprocessing module operable to: detect a variance of the one or more RFcharacteristics from a desired value of the one or more RFcharacteristics; in response to the detecting of the variance, adjustthe tuning circuit to substantially re-establish the desired value ofthe one or more RF characteristics; and generate a message regarding theadjusting of the tuning circuit, wherein a level of the adjusting of thetuning circuit is representative of a variance of pressure sensed by thepressure sensing circuit; and a transmitter operably coupled to transmitthe message.
 2. The wireless sensor of claim 1, wherein the pressuresensing circuit comprises: a variable capacitance circuit that includesa first plate, a second plate, and a diaphragm, wherein, as a result ofpressure variations on the diaphragm, causes a change in capacitance ofthe variable capacitance circuit.
 3. The wireless sensor of claim 1,wherein the pressure sensing circuit comprises: a variable capacitancecircuit that includes a first plate, a second plate, and a diaphragmpuck, wherein, as a result of pressure variations on the diaphragm puck,causes a change in capacitance of the variable capacitance circuit. 4.The wireless sensor of claim 1, wherein the pressure sensing circuitcomprises: a variable inductance circuit that includes a tuning loop anda diaphragm that, as a result of pressure variations, causes aninductance change of the tuning loop.
 5. The wireless sensor of claim 1,wherein the pressure sensing circuit comprises: a variable inductancecircuit that includes a tuning loop and a diaphragm puck that, as aresult of pressure variations, causes an inductance change of the tuningloop.
 6. The wireless sensor of claim 1, wherein an RF characteristic ofthe one or more RF characteristics comprises: an impedance at afrequency; a resonant frequency; a quality factor; and a gain.
 7. Thewireless sensor of claim 1, wherein the processing module is furtheroperable to: in response to a calibration request at a known pressure,adjust the tuning circuit to establish the desired value of the one ormore RF characteristics; and record a level of the adjusting of thetuning circuit to represent a pressure calibration of the wirelesssensor.
 8. The wireless sensor of claim 1 further comprises: a secondantenna; and a power harvesting circuit operably coupled to the secondantenna, wherein, when the second antenna receives an RF signal, thepower harvesting circuit converts the RF signal into a power supplyvoltage.
 9. The wireless sensor of claim 1 further comprises: atemperature sensor operably coupled to the processing module, whereinthe temperature sensor senses a temperature of an environment proximalto the wireless sensor, and wherein the processing module includes asensed temperature within the message.
 10. A passive wireless tirepressure sensor comprises: an antenna; a tuning circuit operably coupledto the antenna; a pressure sensing circuit operably coupled to at leastone of the antenna and the tuning circuit, wherein the antenna, thetuning circuit, and the pressure sensing circuit collectively have oneor more radio frequency (RF) characteristics and wherein the pressuresensing circuit causes the one or more RF characteristics to vary withvarying sensed pressures; a second antenna; a power harvesting circuitoperably coupled to the second antenna, wherein, when the second antennareceives an RF signal, the power harvesting circuit converts the RFsignal into a power supply voltage; a processing module powered via thepower supply voltage, wherein the processing module is operable to:detect a variance of the one or more RF characteristics from a desiredvalue of the one or more RF characteristics; in response to thedetecting of the variance, adjust the tuning circuit to substantiallyre-establish the desired value of the one or more RF characteristics;and generate a message regarding the adjusting of the tuning circuit,wherein a level of the adjusting of the tuning circuit is representativeof a variance of pressure sensed by the pressure sensing circuit; and atransmitter powered by the power supply voltage, wherein the transmittertransmits the message.
 11. The passive wireless tire pressure sensor ofclaim 10, wherein the pressure sensing circuit comprises: a variablecapacitance circuit that includes a first plate, a second plate, and adiaphragm, wherein, as a result of pressure variations on the diaphragm,causes a change in capacitance of the variable capacitance circuit. 12.The passive wireless tire pressure sensor of claim 10, wherein thepressure sensing circuit comprises: a variable capacitance circuit thatincludes a first plate, a second plate, and a diaphragm puck, wherein,as a result of pressure variations on the diaphragm puck, causes achange in capacitance of the variable capacitance circuit.
 13. Thepassive wireless tire pressure sensor of claim 10, wherein the pressuresensing circuit comprises: a variable inductance circuit that includes atuning loop and a diaphragm that, as a result of pressure variations,causes an inductance change of the tuning loop.
 14. The passive wirelesstire pressure sensor of claim 10, wherein the pressure sensing circuitcomprises: a variable inductance circuit that includes a tuning loop anda diaphragm puck that, as a result of pressure variations, causes aninductance change of the tuning loop.
 15. The passive wireless tirepressure sensor of claim 10, wherein the processing module is furtheroperable to: in response to a calibration request at a known pressure,adjust the tuning circuit to establish the desired value of the one ormore RF characteristics; and record a level of the adjusting of thetuning circuit to represent a pressure calibration of the wireless tirepressure sensor.
 16. The passive wireless tire pressure sensor of claim10, wherein the power harvesting circuit is further operable to:converts the RF signal into a first power supply voltage for poweringthe processing module; and converts the RF signal into a second powersupply voltage.
 17. The passive wireless tire pressure sensor of claim10 further comprises: a temperature sensor operably coupled to theprocessing module, wherein the temperature sensor senses a temperatureof an environment proximal to the wireless tire pressure sensor, andwherein the processing module includes a sensed temperature within themessage.
 18. The passive wireless tire pressure sensor of claim 10further comprises: the second antenna being physically mounted on a stemof a tire such that at least a portion of the second antenna is on anoutside of the tire; and the antenna and the pressure sensing circuitare mounted within the tire.